Multi-hop networks are useful in many situations where network infrastructure either does not exist or cannot be trusted. Examples include military operations, disaster relief, and temporary offices. Multi-hop networks (also called packet radio networks, ad hoc networks, or mesh networks) typically use radio frequency (RF) transceivers to send and receive data. In a multi-hop network, nodes in the network typically include a “forwarding” module that performs the functions of:                1. Accepting packets from the lower layer radio, the upper layer Internet Protocol (IP) protocols, or the network control protocols.        2. Using the final destination(s) and type of service (ToS) bits in the packet to determine the appropriate next hop(s) in the network.        3. Determining the type of service requirements in terms of radio transmission characteristics and queuing discipline.        4. Passing the packet to the correct interface or interfaces for radio transport or dropping the packet.        
In most multi-hop radio systems, this forwarding operation, which is also referred to as a switching operation, is typically faster than the radio transmission to the next-hop(s), so queues need to exist inside a node for holding packets that are waiting to be sent. In a highly mobile multi-hop network, it is not uncommon for the next-hop of a packet to change between the time the packet is initially received and processed and the time the interface is ready for transmitting it to a next-hop. In a system that has long queues between the forwarding next-hop lookup and the transmission of the packet by radio, situations can exist where packets at the head of the queue (next in line for transmission by the radio) have been designated for transmission to next-hops that are no longer reachable by the radio. This causes many re-transmissions to occur since the radio layer does not know that the next-hop is now unreachable. These re-transmissions can further delay other packets already in queue so that their next-hops may now also be unreachable by the time these packets reach the head of the queue.
Therefore, there exists a need for systems and methods that improve routing of data in mobile, multi-hop networks.